This present invention relates to lightweight golf club shafts. More particularly, it concerns an improved composite shaft, a method for its manufacture, and a club made with such a shaft. The invented golf shaft is a laminar structural element in the form of a spirally wound assembly of shaped planar sheets wrapped about a common axis.
The laminar structural element preferably includes several thin plies of pre-impregnated, continuous-fiber material. Preferably, two of the plies are similarly shaped and oriented with the fibers aligned with a particular bias, one of the plies with an approximate 45-degree angle transverse to the longitudinal axis of the laminar structural element and the other ply with an approximate 135-degree angle transverse to the longitudinal axis. A butt reinforcement ply, sandwiched between these two biased plies, has fibers aligned approximately perpendicular to the longitudinal axis. These three plies form a subassembly that is rolled first onto a mandrel that has the approximate shape of the desired golf shaft. Subsequently, at least two additional plies are cut in dissimilar shapes, both aligned in a nearly longitudinal or xe2x80x9czeroxe2x80x9d biased orientation and rolled onto the mandrel and subassembly.
The mandrel and wrapped plies then are baked in an autoclave to fuse the plies together to form the resulting shaft. The resulting lightweight shaft has been found to deliver excellent torque to a golf club head mounted on one end when the shaft is gripped and swung. It is believed that the resulting golf club can reduce the slice of the golf ball thereby greatly improving drive distance and accuracy achievable.
Various constructions of composite golf club shafts are disclosed in U.S. Pat. Nos. 1,226,444, 3,809,403, 4,082,277, 4,097,626, 4,132,579, 4,157,181, 4,757,997, 4,889,575, 5,088,735, 5,093,162, 5,245,779, 5,265,872, 5,316,299, 5,326,099, 5,385,767, 5,421,573, 5,427,373, and 5,551,691, the disclosures of which are all incorporated herein by reference. The use of carbon- or boron-based impregnated sheet material in a wrapped laminar structure that forms a thin-walled but very strong golf club shaft are described and illustrated in my U.S. Pat. Nos. 5,569,099 and 5,788,585, the disclosures of which also are incorporated herein by reference.
The advantages of the present invention will be understood more readily after a consideration of the figures and the detailed description.